1. Field of the Invention
The present invention relates to telephone line test termination devices and, in particular, to a circuit arrangement which may be utilized by the central test office to provide an audio-visual signal when being interrogated and a subscriber test to indicate the operability of the subscriber line.
2. Discussion of the Relative Art
Many different types of circuit arrangements have been suggested for use in testing telephone subscriber lines from a remote location. Generally, these circuit arrangements require installation or must be utilized by a telephone installer who must physically visit the premises where the telephone is installed and then signal the central office so that the central office test operator may perform the required test to determine if the subscriber lines are in working order. Many of these circuit arrangements include a switching device and a tuned circuit which is activated from the central office. These components are unreliable and require an installer to enter the home where the telephone is located. This is unsatisfactory for numerous reasons. Generally, the devices are unable to remain permanently at the installed telephone, or if they are capable of being installed permanently, they require activation by an AC signal provided by the central office. None of the devices heretofore are capable of providing a visual indication in addition to an audible signal at the premises where the telephone is installed during the testing of the subscriber lines by the central office test operator. Requiring a telephone installer to enter the customer's premises or requiring activation of the equipment by a superimposed signal from the central office is an unreliable method and therefore is unsatisfactory.
A simple reliable means of providing a circuit arrangement which may be utilized by the central office test operator together with a customer and that is capable of providing an audible signal and visual indication to the customer when being interrogated by the central office to indicate that the subscriber line is intact and operable by merely utilizing a DC test voltage, a milliammeter and a reversing switch, is an ideal solution to the problem. Moreover, providing means for the subscriber to observe a meter reading by pushing an intermittent test button and/or obtain a dial tone, without the use of a telephone instrument to further verify the operability of the subscriber line is even more desirable.